Electro-physiology (1896-98) Electro-physiology . electrophysiolog02bied Year: 1896-98 IX ELECTRICAL EXCITATION OF NERVE 123 currents of exceedingly rapid onset, and induced currents have a powerful excitatory action, even at low intensity, from the same reason. This tendency of the ordinary nerve-muscle preparation to react to the weakest currents, provided they are adjusted with sufficient rapidity, renders it a valuable indication of the presence of weak currents of brief duration (action currents in the muscle). An interesting fact in this connection, and one that also depends mainly upon
Electro-physiology (1896-98) Electro-physiology . electrophysiolog02bied Year: 1896-98 IX ELECTRICAL EXCITATION OF NERVE 123 currents of exceedingly rapid onset, and induced currents have a powerful excitatory action, even at low intensity, from the same reason. This tendency of the ordinary nerve-muscle preparation to react to the weakest currents, provided they are adjusted with sufficient rapidity, renders it a valuable indication of the presence of weak currents of brief duration (action currents in the muscle). An interesting fact in this connection, and one that also depends mainly upon the influence which the onset of any current exerts upon its excitatory action, is the unequal effect of the make and break shock from an induction apparatus. The excitatory action of the make shock is without exception much lower than that of the break. This is plainly seen when the secondary coil is a long way off from the primary. There is always a point at which the break shock is effective, when the make shock fails to excite; on approximating the coils, the latter also takes effect. Since, as is easily shown on the galvanometer, the quantities of electricity in the make and in the break shock are equal, the dissimilarity of physiological effect must be fundamentally due to the differences in time-distribution of the two induction currents, caused by the appearance of the extra cur- rent on closure of the primary circuit. Since the primary current ,11 -i FIG. 174.—Schema of induction currents. in the last case does not _ at once Pj> Abscissa of primary current; s> reach its full strength, but increases gradually, while it suddenly dis- appears on opening the circuit, the induced current must rise more abruptly at break than at make of the primary circuit (Fig. 174). Accordingly, the break shock gives a sharp ' crack ' in the telephone, the make shock, on the contrary, yields a dull, weak sound (Griitzner). This inequality of physiological action in the make and br
Size: 1643px × 1218px
Photo credit: © Bookend / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
